Many underground installations require the completion of digging operations prior to installing pipes, drains, tile equipment, and the like. The digging is often completed with a trencher, a specialized digging apparatus that often includes a chain or some other kind of plowing instrument to break through the ground. The trencher accomplishes just what its name implies—it leaves behind a trench of known size into which numerous kinds of tile drainage or other materials are installed. Trenchers come in a multitude of sizes with various kinds of accessories. While some models are integral with a large piece of construction equipment, one of the most popular kinds of trenchers is releasably attached to a tractor that pulls the trencher. The trencher attaches to the tractor for not only stability and mobility purposes, but the trencher also connects to the tractor's power systems via a transmission box and hydraulic attachments. In one embodiment, the transmission box translates power from the tractor's engine to a motor in the trencher. The motor drives the trencher's digging chain that breaks up the earth to form the necessary trench.
One useful technology in detachable trenchers includes the hydraulic systems that allow the user to change the position of the trencher depending upon the installation at hand. Hydraulic cylinders connected between the tractor and the trencher engage the hydraulic fluid systems on the tractor. Controls allow the user to manipulate the hydraulic cylinders to lift the trencher for digging depth adjustment or to rotate the trencher for angular adjustment.
The lifting and angular position controls have been the subject of prior efforts in the field of tractor-driven trenchers. U.S. Pat. No. 4,142,817 (Lazure 1971) shows hydraulic cylinders that adjust the tilt and vertical position of an attached plow. The cylinders are arranged along with mechanical linking segments to create parallelogram-shaped support structures. The cylinders are used to deform the parallelogram in various directions to move the trencher to an appropriate position for the task at hand.
U.S. Pat. No. 4,750,280 (Dalaine 1988) describes a trencher attachment that tilts about the back tire of the associated tractor pulling the trencher. The trencher moves vertically via a connection to a sleeve that pulls the digging mechanism up and down.
U.S. Pat. No. 5,975,804 (Bockman 1999) discloses a tile plow positioned by front and rear hydraulic cylinders. When the hydraulic cylinders are retracted, a beam is lowered such that the tile plow moves to the lowered plowing position. When the hydraulic cylinders are extended, the beam raises up so that the tile plow moves to a raised transport position. Again, hydraulic cylinders perform the work of moving the trencher to the necessary position.
U.S. Pat. No. 3,575,006 (Rugroden 1971) utilizes arms that are connected to a tractor mount through a pair of hydraulic cylinder and piston members respectively. The piston and cylinder mechanisms are secured pivotally to a fixed arm at upper ends to move the trencher up off the ground or down into a hole.